From DE 10 2010 041 550 A1, a hydraulic feed device is known which has a pendulum-slide cell pump in which an internal rotor is drivingly connected to an external rotor via pendulum slides. Furthermore, the known hydraulic feed device is provided with a hydraulic positioning device for changing eccentricity between internal rotor and external rotor, which has a positioning element for adjusting the eccentricity. Furthermore, the positioning element is preloaded by means of a spring device for setting a maximum eccentricity.
In the case of a pendulum-slide cell pump, the feed rate, besides the speed, is also determined through the eccentricity between the internal rotor and the external rotor. The greater the eccentricity, the higher the feed rate is. In contrast, if the internal rotor and the external rotor are arranged concentrically, the feed rate is reduced to the value “0”, regardless of the speed.
Such hydraulic feed devices can be used in motor vehicles so as to drive a hydraulic working means, preferably oil, in a hydraulic system of the vehicle. Of particular interest are combined hydraulic systems comprising at least two different hydraulic circuits that are assigned to different functions. For example, a primary circuit for actuating a hydraulically actuatable clutch can be coupled with a secondary circuit for supplying lubrication points with oil. The different hydraulic circuits have different requirements in terms of the necessary hydraulic pressure. While lubricating oil supply only needs a constant, comparatively low oil pressure, a clutch may require a varying oil pressure. For example, for shifting the clutch, the oil pressure can be temporarily raised to a high level.
For reducing costs it is desirable to use only a single common hydraulic feed device in such a combined hydraulic system so as to provide both hydraulic circuits with the required hydraulic pressure, wherein the different pressure requirements are to be considered. For this purpose it is principally possible to equip the hydraulic system with a comparatively complex arrangement of control and regulating valves in order to be able to implement the desired hydraulic pressures in both hydraulic circuits. However, the costs for this are comparatively high.